Segmented End Electrode Capacitor and Method of Segmenting an End Electrode of a Capacitor

ABSTRACT

An exemplary embodiment providing one or more improvements includes a capacitor with a segmented end electrode and methods for segmenting an end electrode of a capacitor for reducing or eliminating instances of thermally induced damage of the capacitor.

RELATED APPLICATIONS

This is a divisional application of co-pending prior U.S. patentapplication Ser. No. 11/495,447, filed on Jul. 28, 2006; which claimspriority from U.S. Provisional Application Ser. No. 60/595,783, filed onAug. 5, 2005; the disclosures of which are incorporated herein byreference.

BACKGROUND

Many modern capacitors are made using a capacitor body with metallizedfilm. The metallized film typically includes a thin polymer film such aspolypropylene on which a thin metal film has been condensed or otherwisedeposited. The metallized film is arranged in a manner in which the thinmetal films form two separate internal electrodes that are separated bythe polymer film. The two separate internal electrodes are substantiallyelectrically isolated from one another and a capacitance is exhibitedbetween the internal electrodes. The thin metal film of each internalelectrode is connected to an end electrode and terminations areconnected to each end electrode to electrically connect to thecapacitor.

In some instances, two separate sheets of metallized film are rolled orwound together into a cylindrical shaped capacitor body having twogenerally circular ends. The sheets of metallized film are offset fromone another so that each separate sheet only extends all the way to oneof the generally circular ends. In these instances, each end electrodeis positioned at one of the generally circular ends and is connected tothe sheet of metallized film that extends to the end where the endelectrode is positioned. This construction yields an annular formcapacitor that has a cross-section with layers of metallized film thatalternate between the two separate internal electrodes formed by thethin metal film of each sheet. In this instance, each of the endelectrodes connects together the layers of the respective internalelectrodes.

In other instances, each of the internal electrodes is formed ofseparate layers of the metallized film to create a rectangular shapedcapacitor body. In these instances the layers of one internal electrodeare arranged to alternate with the layers of the other internalelectrode and are offset from one another on two ends. The endelectrodes in these instances, provide an electrical connection betweenthe individual layers of each internal electrode at the offset ends.Other types of capacitors have layers of metal and dielectric such aspolymers, in various arrangements, which are not affixed to one anotherprior to the assembly of the capacitor.

One common technique that is used to create the end electrodes is calledend spray. In this technique a molten end spray metal, which may includetin, zinc or other conductive materials, is sprayed onto each of theoffset ends of the layers of metallized film. The spray continues untilthe end spray metal builds up to a certain thickness. The end spraymetal sticks to the metallized film and, when the molten metal cools andsolidifies, the end spray metal is electrically connected to the metalof the metallized film. The solidified end spray metal on each endconnects to one of the internal electrodes where they serve as the endelectrodes. Typically, the end spray metal is sprayed onto the ends ofthe metallized film in as uniform a manner as possible. Other techniquesfor creating metal end electrodes may also be available.

One of the problems encountered in the use of metal or other types ofrigid end electrodes relates to the failure of the capacitor due to oneor both of the end electrodes cracking. Many cracking problems arethermally induced as a result of the capacitor being subjected totemperature changes and repeated temperature cycling. In some instances,thermally induced cracking includes the condition where one or both endelectrodes at least partially separate from the internal electrodes ofthe capacitor body. Such a separation changes the characteristics of thecapacitor, such as the capacitance and/or current carrying or othercharacteristics of the capacitor. Other types of thermally inducedcracking or damage involve the end electrodes themselves cracking intopieces.

Operation of the capacitor in environments where wide ranges oftemperatures are encountered exacerbates the problems with thermallyinduced cracking. Some environments, which include some types of tests,subject the capacitor to temperatures ranging from −50° C. to 100° C.When the capacitor is heated, through external and/or internalinfluences, the layers and end electrodes of the capacitor expand; andwhen the capacitor is cooled, the layers and end electrodes contract.

In many instances, the cracks are a direct result of the dielectrichaving a different Coefficient of Thermal Expansion (CTE) than the CTEof the end electrode. In some instances, the CTE of the dielectric is anorder of magnitude greater than the CTE of the end electrode. When theCTE of the dielectric is greater than the CTE of the end electrode, thedielectric expands at a greater rate than does the end electrode. Thiscan cause the internal electrodes surrounded by the dielectric to bepulled away from the end electrodes.

Typically capacitors are subject to heat generated externally to thecapacitor and internal to the capacitor. External heating comes from thedevices and atmosphere surrounding the capacitor which typically causesa more or less uniform heating of the capacitor. On the other hand,internal self heating is caused by electrical losses inside thecapacitor. Internal self heating can cause the metallized film or otherinternal electrode and dielectric to be subjected to a highertemperature than the end electrodes. This situation leads to more rapidfailure of the capacitor since the increased temperature experienced bythe metallized film causes the metallized film to expand more than theend electrodes, thereby typically causing the end electrodes to break orcausing other damage to the capacitor.

In some circumstances, some portions of the inside of the capacitorbecome hotter than other portions of the inside of the capacitor. Inthese situations, the metallized film expands more in the hotterportions than in the cooler portions which causes a non-uniform stresson the end electrodes which can lead to capacitor failure.

The rigid end electrodes of some capacitors can be very large, sometimesexceeding ten or more inches in diameter for a cylindrically shapedcapacitor, for instance. These large capacitors have many layers ofdielectric material which, when heated, expand together to increase theoverall dimensions in one or more directions of the capacitor. Theoverall expansion of each dimension of the dielectric is greater thanthe overall expansion of each corresponding dimension of the rigid endelectrodes. Therefore, since the dielectric and rigid end electrodes areconnected to one another but the dielectric is expanding faster than theend electrodes, the end electrodes crack. Thermally induced crackinghappens to small capacitors as well as large capacitors, althoughthermally induced cracking may be more pronounced in large capacitors.

The foregoing examples of the related art and limitations relatedtherewith are intended to be illustrative and not exclusive. Otherlimitations of the related art will become apparent to those of skill inthe art upon reading of the specification and a study of the drawings.

SUMMARY

The following embodiments and aspects thereof are described andillustrated in conjunction with systems, tools and methods which aremeant to be exemplary and illustrative, not limiting in scope. Invarious embodiments, one or more of the above-described problems havebeen reduced or eliminated, while other embodiments are directed toother improvements.

A method for manufacturing a capacitor is described in the presentdisclosure. The method allows the capacitor to resist thermally induceddamage. In the method, a capacitor is formed by positioning a firstelectrically conductive layer in a spaced apart relationship with asecond electrically conductive layer using a dielectric material inbetween the first and second layers. The first layer has a first layerlengthwise edge at a first end of the capacitor body and the secondlayer has a second layer lengthwise edge at a second, opposing end ofthe capacitor body. An end spray metal is sprayed into contact with thefirst layer lengthwise edge at the first end of the capacitor body tocreate a first end electrode and the end spray metal is sprayed intocontact with the second layer lengthwise edge at the second end of thecapacitor body to create a second end electrode. The end spray metal hasa coefficient of thermal expansion that is different than a coefficientof thermal expansion of the dielectric material. The first end electrodeis divided into first electrode segments which are each electricallyconnected to different portions of the first layer lengthwise edge atthe first end. The first electrode segments are arranged to allow thedielectric material to thermally expand and contract while the segmentsremain electrically connected to the different portions of thelengthwise edge at the first end. The first electrode segments areconnected together with flexible electrical conductors to electricallyconnect the first electrode segments together while allowing the firstelectrode segments to move substantially independently from one another.The capacitor exhibits a capacitance between the connected firstelectrode segments and the second end electrode.

Another method disclosed involves a method for reducing thermallyinduced damage in a metallized film capacitor. The capacitor has anarrangement of first and second internal electrodes made with layers ofmetallized film that are electrically isolated from one another. Thefirst internal electrode is electrically connected to a first endelectrode at a first end and the second internal electrode iselectrically connected to a second end electrode at a second end. Thefirst and second end electrodes are substantially rigid and have acoefficient of thermal expansion that is different from a coefficient ofthermal expansion of the metallized film. The end electrodes are dividedinto electrode segments to allow the metallized film to thermally expandand contract while the first internal electrode remains electricallyconnected to the first end electrode and the second internal electroderemains electrically connected to the second end electrode.

Another method involves producing a capacitor with metal end electrodesconnected to a wound metallized film. The metallized film has adielectric that thermally expands and contracts. The end electrodes aredivided into a plurality of electrode segments which can movesubstantially independently from one another while remaining connectedto the metallized film responsive to thermal expansion and contraction.

A capacitor is disclosed which has a first electrically conductive layerhaving a first layer lengthwise edge and a second electricallyconductive layer having a second layer lengthwise edge, where the firstand second electrically conductive layers are arranged in a spaced apartrelationship from one another. A dielectric material is positionedbetween the first and second electrically conductive layers. A first endelectrode is electrically connected to the first layer lengthwise edge,and a second end electrode is electrically connected to the second layerlengthwise edge. The second end electrode is divided into a plurality ofelectrode segments that are each connected to different portions of thesecond layer lengthwise edge. The dielectric material is capable ofthermally expanding and contracting while the electrode segments remainconnected to the second layer lengthwise edge. The capacitor exhibits acapacitance between each of the electrode segments and the first endelectrode.

In addition to the exemplary aspects and embodiments described above,further aspects and embodiments will become apparent by reference to thedrawings and by study of the following descriptions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a capacitor having segmented endelectrodes according to the present disclosure.

FIG. 2 is a section view of the capacitor shown in FIG. 1, taken alongsection line 2-2.

FIG. 3 is another section view of a capacitor according to the presentdisclosure having segmented end electrodes which are electricallyconnected to one another.

FIG. 4 is a perspective view of a capacitor according to the presentdisclosure having segmented end electrodes which are electricallyconnected to one another.

DETAILED DESCRIPTION

A capacitor 20 according to the present disclosure is shown in FIG. 1.Exemplary capacitor 20 includes a capacitor body 22 and two endelectrodes 24 and 26 which are divided into end segments 28 and 30,respectively. Dividing or segmenting end electrodes 24 and 26 allows thesegments to move substantially independently from one another whichavoids or reduces instances of thermally induced cracking of the endelectrodes.

Each of segments 28 and 30 are connected with a different portion ofcapacitor body 22 and are not directly connected to one another with arigid interface. This allows individual segments 28 and 30 to move withexpansion and contraction of the portion of capacitor body 22 to whichthey are connected without causing cracks to form in end electrodes 24and 26.

Since each segment is connected to a different portion of the capacitorbody, each segment is therefore substantially only subject to forcescaused by the connected portion of the capacitor body. The forces arecaused by a relative change in dimension between the segment and theportion of the capacitor body to which it is attached, due to thesegment and capacitor body having different coefficient of thermalexpansions (CTE). By dividing the end electrodes into segments, theseforces are overcome by the strength of the attachment between thecapacitor body and the segments.

Segments include segment edges 32 and segment faces 34, FIGS. 2 and 3.In some instances, the segment edges 32 of adjacent segments may atleast temporarily contact one another, FIGS. 1 and 2. This is notconsidered to affect the substantially independent nature of themovement of the segments relative to one another. Gaps 36 define segmentedges 32 between adjacent segments. In other instances, segment edges 32of adjacent segments 28 or 30 do not contact one another at anytemperature, FIG. 3. In these instances, gap 36 is relatively large.Other partially extending gaps 39, FIG. 1, may not be between separateelectrode segments, but may instead extend only partially across anelectrode segment. Partially extending gap 39 may allow the electrodesegment to deform rather than crack when subjected to stress. Otherconfigurations of gaps and segments may also be used for reducing theincidence of thermally induced damage.

As the temperature of the capacitor increases, the segments will movefurther away from one another. The segments move further away from oneanother in these instances because material in capacitor body 22 has ahigher CTE than does the material of the end electrodes 24 and 26. Thissituation causes an increase in the size of gaps 36 between adjacentsegments and limits or eliminates the effect that the movement of onesegment has on the movement of other segments. Therefore, as capacitorbody 22 increases in temperature the body expands at a greater rate thando segments 28 and 30, which causes the segments to be moved away fromone another in a plane of end electrodes 24 and 26.

Capacitor body 22 includes internal electrodes or electricallyconductive layers 38 and 40 and dielectric material or layers 42 and 44,as shown in FIGS. 2 and 3. Electrically conductive layers 38 and 40 arearranged for producing a capacitance. Capacitor body 22 shown in FIG. 1has a cylindrical or annular shape with two circular ends where endelectrodes 24 and 26 are attached to electrically conductive layers 38and 40, respectively. Capacitor body 22, in the present example, definesa cylindrical opening 45.

In some instances, the cylindrically or annular shaped capacitor bodyhas generally circular end electrodes 24 and 26 which are defined by aradius 47 that extends from a center point 49. A circularly shaped gap37 can be used with capacitor body 22 where the circular gap is definedby a radius 51 which extends from a center point 53. In this instance,center point 53 can be located at a different position than center point49 so that circular gap 37 is not concentric with generally circular endelectrode 24. The non-concentric nature of circular gap 37 prevents thegap from being generally co-linear with electrically conductive layers38 or 40 for any substantial length which limits the distance thatelectrical current must flow along a length of electrically conductivelayer 38 or 40 before reaching end electrode 24 or 26.

In the case of cylindrically shaped capacitor body 22 of the presentexamples, the body is formed by rolling together two sheets 46 and 48 ofmetallized film. Metallized film 46 and 48 has a film portion whichserves as dielectric 42 and 44, respectively, and a metal layer havingdeposited thereon a thin coating on the film portion and which serves asthe electrically conductive layers 38 and 40, respectively. Typically,the film portion is a type of polymer and the metal is deposited on thepolymer by condensing a metal vapor. Multiple layers of electricallyconductive layers 38 and 40 and dielectric 42 and 44 are displayed in across section of cylindrically shaped body 22, as shown in FIGS. 2 and3, however, every other layer 38 or 40 simply represents additionalturns of the sheets 46 and 48, respectively. Capacitor body 22, shown inFIGS. 2 and 3, increases in radius in the direction of arrow 54.

The two sheets 46 and 48 are rolled together to form capacitor body 22,in the present example, in such a way that electrically conductive layer38 extends to a lengthwise edge 50 of sheet 46 and electricallyconductive layer 40 extends to a lengthwise edge 52 of sheet 48 as shownin FIGS. 2 and 3. Electrically conductive layers 38 are connected to endsegments 28 of end electrode 24 along lengthwise edge 50.

Other methods of constructing capacitor body 22 into the cylindrical orother shapes may also be used. For example, separate layers ofelectrically conductive material and dielectric may be used, and thecapacitor body may be formed with a rectangular shape.

End electrodes 24 and 26 are typically attached to capacitor body 22 byspraying an end spray metal onto the lengthwise edges 50 and 52,respectively. In this spraying process, the end spray metal is heated toa molten state and droplets of the metal are deposited onto edges 50 and52 where contact is made with electrically conductive layers 38 and 40,respectively. Metals used for the end spray metal include tin, zinc,and/or others. The droplets of end spray metal are deposited oncapacitor body 22 until the end electrodes are sufficiently thick. Insome examples, sufficient thickness occurs when the end electrodes arethick enough to withstand connection of flexible electrical conductors56 (FIG. 3) at connection points 58 on the faces 34 of the endelectrodes 24 and 26. As an example, the thickness of the sprayedelectrodes in some capacitors is typically 0.005″ to 0.025″ thick.

In some instances, end electrodes 24 and 26 are segmented or divided byusing a mask with the spraying process. In these instances, the mask isplaced relative to lengthwise edges 50 and 52 of capacitor body 22during the spraying process. The mask may have metal rods or spokeswhich block the droplets end spray metal from reaching portions oflengthwise edges 50 and 52 of electrically conductive layers 38 and 40which leaves gaps 36 in end electrodes 24 and 26. Segments 28 and 30 areformed with the end spray metal where the mask does not block thedroplets from contacting lengthwise edges 50 and 52. Other materials andmasking techniques may be used to create end electrodes 24 and 26 withsegments 28 and 30.

Segments 28 and 30 may also be created by sawing or otherwise cuttingthe end electrodes 24 and 26 after the end electrodes are connected orformed on capacitor body 22 as solid or undivided pieces. In oneinstance, a circular saw blade is used to cut gaps 36 in end electrodes24 and 26 to create the segments 28 and 30. Some segments 28 and 30 aredivided with an arrangement where at least some gaps 36 run along aradius of a circularly shaped end electrode. Other segment patterns orarrangements may also be used so long as the segments reduce theinstance of cracking of the end electrodes. Some patterns orarrangements of segments may be better at reducing or eliminatingthermally induced damage than other patterns or arrangements ofsegments. This may depend, at least in part, on the directions in whichcapacitor body 22 expands the greatest when heated. It is consideredthat one of ordinary skill in the art can accomplish forming segments ina suitable manner such as, for example, by using a mask, sawing or inany other suitable way, with this disclosure in hand.

The number of segments is based at least partially on the size of endelectrodes 24 and 26, in some instances. Larger end electrodes generallyrequire more segments than do small end electrodes. Typically, moresegments yield a decreased risk of thermally induced damage than doesfewer segments for a given size of end electrode. However, there arepractical limits on the number of segments which the end electrodes canbe divided into, since it is typically more difficult to attach flexibleconductors 56 to smaller segments. As an example, a cylindrical orannular shaped capacitor having an end electrode with a diameter ofapproximately ten inches, may have 12 to 24 separate electrode segmentson each end. These or other end electrodes may have more or lesssegments, and the number or arrangement of segments on each endelectrode of a single capacitor may be different.

Segments 28 and 30 shown in FIG. 3 are attached to buses 60 and 62 withflexible electrical conductors 56. Buses 60 and 62 are relatively rigidand flexible electrical conductors 56, shown in FIG. 3, are made ofbendable metal which allows the segments to move relative to one anotherwithout breaking loose from busses 60 and 62. Flexible electricalconductors 56 electrically connect segments 28 to buses 60 andelectrically connect segments 30 to bus 62. Buses 60 and 62 serve asterminals to connect capacitor 20 to other electrical components (notshown).

Flexible electrical conductors 56 shown in FIG. 4 are made of braidedwires. Flexible electrical conductors 56, in this instance, electricallyconnect adjacent segments 28 to one another and adjacent segments 30 toone another at connection points 58. In this arrangement, all ofsegments 28 are electrically connected to one another to serve as endelectrode 24; and all of the segments 30 are electrically connected toone another to serve as end electrode 26. Flexible cables 64 and 66serve as terminals to electrically connect each end electrode 24 and 26of the capacitor 20 to other electrical components.

In addition, or as an alternative to having all of the segmentselectrically connected together, each of the segments 28 and 30 can eachhave independent flexible terminals and/or the segments can be organizedin groups which are electrically connected together. In some instances,the terminals are connected together externally to the capacitor. Insome instances, the capacitor may have only one end electrode dividedinto segments. Generally, connections to segments 28 and 30 should havea flexible nature which does not unduly interfere with the movement ofone segment relative to the other segments.

An added benefit experienced by connecting an independent flexibleterminal to each of the segments is that the equivalent seriesinductance (ESL) of the capacitor is reduced in comparison to similarcapacitors which do not have independent terminals to each segment.Reduction of ESL is important because it improves the ability of acircuit to reduce ripple on a power bus. When each segment is connectedto the power bus with a separate terminal, each segment behaves as aquasi-discrete capacitor. This causes an overall ESL of the capacitor tobe reduced relative to an identical capacitor having a single continuousend electrode with a single terminal on each end of the capacitor.

Segmenting one or more of the end electrodes improves the reliability ofthe capacitor by reducing or eliminating the incidences where thecapacitor fails or degrades due to thermally induced damage. Affects ofCTE mismatch are mitigated by separating the end electrodes intosegments which reduces forces acting to damage the end electrodes. Thesegments reduce or eliminate the effects that expanding portions of onepart of the capacitor body have on segments which are not connected tothe part of the capacitor body. Segmenting the end electrodes allows thesegments to move in different directions and/or at different rates fromone another, which reduces the stress between different portions of theend electrodes. Segmented end electrodes can be used on capacitors witha metal or rigid interface between capacitor internal electrode layersand external connections.

While a number of exemplary aspects and embodiments have been discussedabove, those of skill in the art will recognize certain modifications,permutations, additions and sub-combinations thereof. It is thereforeintended that the following appended claims and claims hereafterintroduced are interpreted to include all such modifications,permutations, additions and sub-combinations as are within their truespirit and scope.

1. A method for manufacturing a capacitor which resists thermallyinduced damage, the method comprising: forming a capacitor body bypositioning a first electrically conductive layer in a spaced apartrelationship with a second electrically conductive layer using adielectric material in between the first and second layers, said firstlayer having a first layer lengthwise edge at a first end of saidcapacitor body and said second layer having a second layer lengthwiseedge at a second, opposing end of said capacitor body; spraying an endspray metal into contact with the first layer lengthwise edge at thefirst end of the capacitor body to create a first end electrode andspraying the end spray metal into contact with the second layerlengthwise edge at the second end of the capacitor body to create asecond end electrode, the end spray metal having a coefficient ofthermal expansion that is different than a coefficient of thermalexpansion of the dielectric material; dividing the first end electrodeinto first electrode segments which are each electrically connected todifferent portions of the first layer lengthwise edge at the first end,the first electrode segments arranged to allow the dielectric materialto thermally expand and contract while the segments remain electricallyconnected to the different portions of the lengthwise edge at the firstend; and connecting the first electrode segments together with flexibleelectrical conductors to electrically connect the first electrodesegments together while allowing the first electrode segments to movesubstantially independently from one another, where the capacitorexhibits a capacitance between the connected first electrode segmentsand the second end electrode.
 2. A method as defined in claim 1, furthercomprising: dividing the second end electrode into second electrodesegments which are each electrically connected to a different portion ofthe second layer lengthwise edge at the second end to allow thedielectric material to thermally expand and contract while the secondelectrode segments remain connected to the second layer lengthwise edge;and connecting the second electrode segments together with flexibleelectrical conductors to electrically connect the second electrodesegments together while allowing the second electrode segments to movesubstantially independently from one another, where the capacitorexhibits said capacitance between the connected first electrode segmentsand the connected second electrode segments.
 3. A method as defined inclaim 1 wherein a metallized polymer film is used in forming theelectrically conductive layers and the dielectric.
 4. A method asdefined in claim 1 wherein the first end electrode is divided into firstelectrode segments by sawing the first end electrodes.
 5. A method asdefined in claim 1 wherein the first end electrode is divided into firstelectrode segments by masking the first end of the capacitor body beforespraying the end spray metal into contact with the first layerlengthwise edge.
 6. A method as defined in claim 5 wherein the first endis masked with a metal mask which includes metal rods.
 7. A method asdefined in claim 1 wherein the end electrodes are divided using a cuttertip.
 8. A method as defined in claim 1 wherein the first end electrodehas a generally circular shape defined by a first radius extending froma first center point and the first electrode segments include a segmentcircular shape that is defined by a second radius extending from asecond center point, where the first and second center points are atdifferent locations.
 9. A method for reducing thermally induced damagein a metallized film capacitor having an arrangement of first and secondinternal electrodes made with layers of metallized film that areelectrically isolated from one another and where the first internalelectrode is electrically connected to a first end electrode at a firstend and the second internal electrode is electrically connected to asecond end electrode at a second end, where the first and second endelectrodes are substantially rigid have a coefficient of thermalexpansion that is different from a coefficient of thermal expansion ofthe metallized film, the method comprising: dividing the end electrodesinto electrode segments to allow the metallized film to thermally expandand contract while the first internal electrode remains electricallyconnected to the first end electrode and the second internal electroderemains electrically connected to the second end electrode.
 10. A methodas defined in claim 9 wherein the end electrodes are divided intosegments by sawing the end electrodes after the end electrodes arespraying onto the internal electrodes in a molten state.
 11. A method asdefined in claim 9 wherein the end electrodes are divided into electrodesegments by masking the ends of the internal electrodes and spraying theend electrodes into contact with the internal electrodes on the ends.12. A method as defined in claim 11 wherein the segments are masked witha metal mask which includes metal rods.
 13. A method as defined in claim9 wherein the end electrodes are divided using a cutter tip.
 14. Amethod as defined in claim 9 further comprising electrically connectingelectrode segments of one end together with one another and electricallyconnecting electrode segments of the other end together with oneanother, where the electrode segments of one end are electricallyisolated from the electrode segments of the other end.
 15. A method asdefined in claim 9 wherein the metallized films are arranged inalternating layers by rolling the metallized films into a generallycylindrical shape.
 16. In producing a capacitor with metal endelectrodes connected to a wound metallized film having a dielectric thatthermally expands and contracts, a method comprising: dividing each ofthe end electrodes into a plurality of electrode segments which can movesubstantially independently from one another while remaining connectedto the metallized film responsive to thermal expansion and contraction.17. A method as defined in claim 16, further comprising: connecting theelectrode segments of each end electrode to one another electricallywith one or more flexible electrical connectors.
 18. A method as definedin claim 16 wherein the electrode segments are connected to one anotherelectrically using one or more braided cable electrical connectors. 19.A method as defined in claim 16 wherein the end electrodes are dividedusing a cutter tip.
 20. A method as defined in claim 16 wherein themetal end electrodes have a generally circular shape defined by a firstradius extending from a first center point and the segments include asegment circular shape that is defined by a second radius extending froma second center point, where the first and second center points are atdifferent locations.